Circuit interrupter



Aug. 25, 1953 E. c. GRoNcwsKl CIRCUIT INTERRUPTER Filed Aug. 3, 1951 @ww/a IN VEN TOR.

Patented Aug. 25, 1953 UNITED STATES PATENT OFFICE CIRCUIT IN TERRUPTER Application August 3, 1951, Serial No. 240,193

11 Claims'. (Cl'. I300-129) This invention relates to cutouts for electrical circuits, and more particularly pertains to a mechanism designed for use in conjunction with expulsion fuses of the plug and socket, or bayonet type, wherein the fuse unit may be subjected to a considerable recoil force on overload, and must be secured against expulsion from the housing in which it is normally mounted-the recoil often being suiiicient to expel the fuse unit with considerable violence, if it is not adequately secured.

As ordinarily constructed, the bayonet-type cutout is diincu-ltand dangerous to operate, as it is entirely feasible thata lineman mayplug into a short-circuited." line, thereby receiving the full force of the expulsion directly into his hand. In addition, it is important that the unit containing the fuse be capable of Withdrawal from the housing with little diiliculty, asY these protective devicesare generally mounted' near' the ends of cross-arms where they can be reached by liner-nen only with considerable stretching.

The primary' object of the presentinvention is to provide a simple, yet effective locking mechanism which operates automatically tol prevent expulsion of the plug unit from the cutout-housing in response to an explosive reaction, and which, at the same time, renders the unit easily withdrawable manually.

Another object of this invention is to provide a locking or clutch mechanism for a bayonet-type fuse cutout that is not dependent upon iluid pressure alone for locking action, but operates in conjunction withV the main spring and cable assembly of the expendable fuse unit, thereby insuring a dependable and positive locking arrangement for preventing expulsion of the plug portion when a blow-out occurs.

The mechanism of the present invention is characterized, in its preferred embodiment, by the use :of a ferrule having diametric'ally opposed passages and a metalv ball in each passage freely movable outwardly into locking contact with an annular depression in a surrounding terminal mounted in the insulating housing. The. fuse link spring assembly may be provided with a. resilient sleeve circumjacent to theV main spring for pushing the balls outwardly into locking position when the sleeve moves upwardly with the spring on overload. When the fuse link isin tension, the sleeve is positioned below the balls andthe fuse assembly may be freely moved within the ferrule. On rupture by excess current, the spring is released and the sleeve moves upwardly to temporarily lock the fuse assembly in position during expulsion. The sleeve continues its upward movement to a position where the balls are again free. The unit can be readily withdrawn manually in response to a steadily applied pull following, or contemporaneo-usly with, a slight rotation which is eiective to break the initial grip between the balls and the annular depression.

In the drawings:

Fig. 1 is a vertical sectional view showing the preferred locking mechanism applied to a conventional plug and socket type expulsion fuse;

Fig. 2 is a fragmentary sectional view showing the upper end of the socket member and the plug member in operative association, with the novel locking mechanism shown in locked position;

Fig. 3V is a fragmentary sectional view similar to Fig. 2 illustrating another embodiment of the novellocking mechanism;

Fig. 4 is a sectional view taken along lines li-4 of Figs. 2 and 3 with the filler cement removed to more clearly disclose the structure of the upper terminal member.

Referring to Fig. l, the novel locking mechanism may be incorporated in a conventional bayonet type fuse cutout which comprises a fuse cartridge IV positioned within the bore 2 of an insulating housing,` or socket member 3. The socket member may be mounted on a cross-arm by means of a clamp (not shown) in the conventional manner, which clamp may be positioned circumferentially of the socket member at the portion 4 intermediate of the ends of the housing.

The bore of the housing 3 is preferably enlarged` at` the two ends to form concentric recesses 5k and 6 and the shoulders l and 8. The exterior of the housing 3 is preferably formed with annular petticoats l which serve to increasel the length of the leakage paths between terminals and between each line terminal and ground.

An upper terminal ring I'I is seated in recess 5, coaxially with the bore 2 and spaced from the shoulder 'l by the flange [-2 of a tubular spring 4contact member i3. The contact member is preferably split lengthwise through a portion of its length; and to insure uniform contacting engagement, a resilient band I4 may be provided at the lower end of the member. A terminal ring l5 is seated in recess 6, coaxially with the bore 2, and spaced from the shoulder 8 by a gasket I6. Rings Il and I5 are anchored in the housing by fillers lvl and I8 of cement or lead. Ring il is apertured transversely at I9 while ring l5 is smilarly apertured transversely at 20, in each case to receive terminals of a line in which the fuse is to be inserted. The housing 3 is provided with transverse openings 2l and 22 registering with aperture I9 (see Fig. 4) and with additional similar openings (not shown) at its lower end registering with aperture 20. It is t-o be noted that the ller cement II is not shown in Fig. 4 in order to more clearly indicate the structure of the component parts positioned in the upper end of the housing 3. Binding screws 23 and 24, threaded respectively into rings Il and I5, serve to firmly secure the line conductor terminals which enter the apertures 2l and 22 through the afore-mentioned transverse openings housing.

Secured to ring I by means of screws 24 and 25 is an inwardly and outwardly vprojecting socket-like tubular spring contact .member 26 which is suitably split lengthwise through a portion of its length to afford lateral resiliency. Upper ring II is provided with an annular depression 30 for engagement with locking balls hereinafter described. In addition, the ring II is preferably counterbored with a conical surface 3| as a convenient means for guiding the fuse cartridge I during insertion of the tube within the bore 2 0f housing 3.

The plug unit includes the fuse cartridge I, and is provided with a suitable insulating handle 32 formed with a skirt-like hood 33, which is adapted to t down over the upper end of the housing or socket member 3, thereby excluding moisture and shielding the operators hand from any possible injury during pulling or inserting the plug member. An insert 34 has at its upper end a ribbed post cemented firmly in place in a recess 35 in the handle by a suitable cement or alloy binder indicated at 35. the insert 34 is slightly enlarged and internally threaded or tapped for receiving the externally threaded upper end 3l of the upper ferrule 38 of the fuse cartridge I. The upper ferrule 33 is preferably counterbored to p-rovide a recess 39 for receiving an insulating tube 40.

The fuse tube 40 may be of horn ber or, alternatively, some other suitable insulation material such as Bakelite lined with horn fiber or lother material capable of evolving arc-extinguishing gas or vapor when subjected to an arc-such material being well-known in the art. To the lower end of the fuse tube 40 is secured a tubular metal ferrule 4I, which is designed for insertion into the socket-like tubular spring contact member 26 for effecting an electrical connection therewith and thereby establishing a circuit between the lower terminal ring I5 and the lower terminal 0f the fuse link. The ferrule 4I is preferably downwardly ared at its lower end, as shown, in order to maintain a free passageway for discharged gases expelled from the interior of the fuse tube. A constricted portion 42, along one side of the passageway, results from locally compressing the ferrule to form a narrowed recess (not shown) for the reception of a fitting 43 attached to the fuse link and referred to hereafter in connection with the description of the fuse link. Notches 44 are also formed in the locally compressed portion 42 lof the flare for the reception of a pin 45 which serves to anchor the lower end of the fuse link and establish electrical contact between the fuse link and the ferrule 4 I.

Any one of well-known fuse link units may be used in the structure with slight modication lof the lower portion of the fuse unit, which does not form a part of the present invention. For purposes of this description, attention is directed to the self-contained replaceable unit shown, which comprises a fusible section consisting The lower end of in the of a fuse wire and a strain wire in parallel and designed to rupture in response to a fault current in excess of a predetermined limit. The upper end of the fusible section is connected to a threaded terminal member 5I while the lower end (not shown) is connected in a well-known manner to the leader 52. There is attached to the flexible leader a conductive fitting 43 having a transverse pin 45 projecting from opposite sides thereof, and designed to seat in notches 44 for the purpose of anchoring the lower end of the fuse-link and establishing electrical connection thereof with the ferrule 4I, and thence with the lower terminalring I5 and the line wire connected therewith.

- They terminal member 5I is connected to a metal coupling member 53 which preferably is provided with a helical groove or other gripping lmeans (not shown) for engagement with the lower few turns of the main fuse spring 54. The opposite end of the spring 54 is grippingly engaged by the contact button 55. A iiexible conductor 56 interconnects the contact button and the coupling member 53.

The spring 54 continuously applies tension to the strain wire of the fusible section by exerting an upward force on the coupling member 53 when the fuse unit is placed in operation with ther transverse pin 45 engaged with the notches 44 of the ferrule 4I.

The novel locking mechanism preferably comprises metal balls 53 which are radially disposed and freely movable within transverse openings or passages 3l of the upper ferrule 38. The diameter of the metal balls is preferably slightly larger than the wall thickness of the tubular ferrule. Three balls are shown in Fig. 4, and are preferably spaced equally around the circumference of the ferrule, a more or lesser number being provided if so required without departing from the scope Lof this invention. The passages 6I are preferably constricted at each end to prevent the balls from rolling out either end after being placed therein.

A fuse unit is readily placed within the fuse cartridge I by simply unscrewing the handle 32 from the cartridge, removing the spent fusible section 50 from the coupling member 53, and replacing it with a new section. After insertion of the replaceable fuse unit within the bore of the insulating tube 40, the handle is again Athreadly engaged with the fuse tube. The leader 52 is preferably made long enough to extend from the bottom of the flared portion of the lower ferrule 4I. Thus, the operator need merely grasp the exible leader 52, stress the spring 54 within the tube 40, and anchor the transverse pin 45 in the notches 44 of the ferrule 4l. Any excess amount of leader may be clipped with a pliers or similar cutting instrument.

The operator next grasps the insulating handle 32 and inserts the plug unit within the bore 2 of the housing or socket member 3. Electrical contact is thereby made between the terminal rings II and I5 through the fuse cartridge I when the plug unit has been inserted as far as it will go. It will be apparent that the diameter 'ofthe convolutions of the spring 54 will be reduced rwhen the spring is under tension with the fuse unit anchored within the fuse tube. The balls 60 will then be free to move in either direction within the passages 5I of the upper ferrule 38. Insertion of the fuse unit I within the bore 2 of the housing 3 may be accomplished without restriction as the freely movablev balls willv move radially inward. The locking device is thus normally in released position as shown in Fig. l, and therefore offers no resistance to free removalor insertion of the fuse unit. It also avoids any necessity for turning of the plug member to lock it in place, and presents no locking parts which are operativeA under normal conditions when the fusehas not been severed by overload.

OperationY of the locking device occurs instantaneously with, or immediately after severance of thefusib'le element. Operationof the novel locking mechanism is brought about by action of eitherl or both of two" forces. It will be obvious that the diameter of the convolutions of the spring 54 will increase on compression of the spring after severanceY of the fuse link. It is preferable to select a spring with convolutions having an external diameter substantially equal to the bore of the` fuse tube ll'JY when the spring is under stress-free retraction.

Referring now to Fig. 2, it will be noted that the convolutions of the spring 511Y expand to substantially ll the bore of the upper ferrule 38 immediately upon retraction of the spring, thereby forcing the balls 60; which preferably slightly protrude from both sides of the wall of the ferrule, radially outwardly towards engagement with the annular depression and the upper terminal ring I I. enough to cause arcing, the arc-extinguishing material of the fusetube will emit deionizing gases andv vapors at considerable pressure. This fluid pressure is the additional force acting on the balls 60 forcing them into engagement with the annular depression until the gas pressure inside the tube is later released. Thus, it will be apparent that one of the distinct advantages to the novel locking mechanism is that at the time when the lock is most needed (when the unit is under vhigh internal pressure), the pressure is also utilized, in addition to the forces exerted by the convolutions of the spring, for engaging thel balls lillY with the annular depression 30.

The plug member is thereby lockedsecurely and positively in place within the bore of the socket member under any fault condition affecting the cutout.

After the fuse has ruptured and the gases created are spent, the only forces exerted against the balls will be those provided by the expanded convolutions of the retracted spring 54. These forces, though ample for locking purposes during interruption of the current, may be easily overcome on Withdrawal of the fuse unit from the housing. The plug member is easily disengaged from the socket member by firmly pulling on the handle 32 of the unit and at the same time rotating the .handle slightly. The balls 60 will thus be forced inwardly between the coils of the contracted spring just enough to disengage them from the annular depression.

It will be apparent that the novel locking mechanism may be positioned independently of the upper terminal structure if so desired. For economical manufacture, it is preferably positioned' as shown with the annular depression provided in the terminal ring Il. In addition, it is preferable to position the plane of the radially expansible balls 60 in a manner that will permit a portion of the retracted spring 54 to protrude below the balls. The convolutions of the spring Will. thereby aidin maintaining engagement of .ne balls and the. annular depression.

On fault currents large It is preferable to` use the radially disposed balls as shown, but it isj within the province. of this invention tov use any radially expansible members that are responsive' to the forces produced by expulsion Within the tube 40, and are further responsive to-action of the tension member of the fusible unit. Various wedges, slidable pins, and the like (notishownl) may be usedl in a manner similar tothe radially disposed balls 60.

Another embodiment of my invention is disclosed in Fig. 3; which shows the ball 60l in engagement With the annular depression 30 of the upper terminal ring` H after the fusibleelement has been ruptured. This-v embodiment is provided where it is desired toha-ve a more positive locking engagement between the balls andv the annularr depression. Referring now to Fig. 3, it will be notedV that-va resilient sleeve 65l is positioned circumjacently tothe coil spring 54". The sleeve 65-may be fas-tened to-thespring 54- inthe conventional manner, and is'shown here positioned in a plane above' the ball 50. Normally, when the spring 54y is under tension with the fusible element anchored in place (not shown), the upper portion of the sleevel isV positioned in a plane below the balls 60. This embodiment of the novel locking mechanism'l operates in a manner substantially identical to the preferred embodiment, but with a more positive action. As the convolutions of the spring 54 retract, and simultaneously expand after severance of the fusible element, they will carry the sleeve 65 upwardly past the balls Bll'to the position shown in Fig. 3. The sleeve isv preferably split, as shown, to expand with the convolutions. Thus the balls will be forced by the sleeve' to abruptly engage with the annular depression 3U. Insertion and withdrawal of the plug unit is accomplished in substantially the same manner as described in connection with the nrst embodiment. The balls 60 are shown in locked position in Fig. 4, which figure is a cross-sectional view relating to both Figs. 2V and 3.

The arrangement of the locking mechanism shown in both embodiments is. simple, positive and effective immediately upon severance of the fusible element. A positive locking engagement of the plug member within its socket member is insured with the mechanism operating under the influence of two effective. locking forces. TheseV forces oppose the` expulsion forces acting to expell the plug member from the bore of the socket member.

I claim:

1. A circuit interrupter comprising plug and socket members provided with cooperating contacts, the plug member being tubular and having a fusible element contained therein and connecting said contacts, said' fusible element being normally biased towards severanceY by a transversely expansible resilient member, the wall of said tubular plug member containing a radially slidable member, said socket member being provided with an annular depression, said slidable member being movable radially outwardly towards engagement with saidV annular depression on contact with saidresilient member on transverse' expansion. of said member after severance of said fusible element, thereby locking said plug member in said socket member.

2. A circuit interrupter comprising plug and socket members provided with cooperating contacts, the plug member being tubular and having a fusible element contained therein and connecting said contacts, said fusible member being normally biased towards severance by a tensioned coil spring, the wall of said tubular plug member containing a radially slidable member, said socket member being provided with an annular depression, said slidable member being movable radially outwardly towards engagement with said annular depression upon contact with the convolutions of said coil spring on retraction of said spring after severance of said fusible element, thereby locking said plug member in said socket member.

3. A circuit interrupter comprising plug and socket members provided with cooperating contacts, said plug member being tubular and having a fusible element contained therein and connecting said contacts, said fusible member being normally biased towards severance by a tensioned coil spring, a resilient sleeve circumjacent to the convolutions of said spring and arranged to move longitudinally of said tubular plug member on retraction of said spring after severance of said fusible element, the wall of said tubular plug member containing a radially slidable member, said socket member being provided with an annular depression, said slidable member being movable radially outwardly towards engagement with said annular depression upon contact with said resilient sleeve after severance of said fusible element, thereby locking said plug member in said socket member.

4. A circuit interrupter comprising plug and socket members provided with cooperating contacts, the plug member being tubular and having a fusible element contained therein and connecting said contacts, said fusible element being normally biased towards severance by a transversely expansible resilient member, the wall of said tubular plug member having radially disposed passages, said socket member being provided with an annular depression, spherical members freely disposed within said passages and being movable radially `outwardly for engagement with said annular depression upon contact with said resilient member on transverse expansion of said member after severance of said fusible element, thereby locking said plug member in said socket member.

5. A circuit interrupter comprising plug and socket members provided with cooperating contacts, said plug member being tubular and having a fusible element contained therein and connecting said contacts, said fusible element being normally biased towards severance by a tensioned coil spring, the wall of said tubular plug member having radially disposed passages, said socket member being provided with an annular depression, spherical members freely disposed within said passages and arranged to be moved radially outwardly for engagement with said annular depression on contact with the convolutions of said coil spring on retraction of said spring after severance of said fusible element, thereby locking said plug member in said socket member.

6. A circuit interrupter comprising plug and socket members provided with cooperating contacts, said plug member being tubular and having a fusible element contained therein and connecting said contacts, said fusible element being normally biased towards severance by a tensioned coil spring, a resilient sleeve circumjacent to the convolutions of said spring and arranged to move longitudinally of said tubular plug member on retraction of said spring after severance of said fusible element, the wall of said tubular plug member having radially disposed passages, said socket member being provided with an annular depression, spherical members freely disposed within said passages and arranged to be moved radially outwardly for engagement with said annular depression upon contact with said resilient sleeve after severance of said fusible element, thereby locking said plug member in said socket member.

7. A circuit interrupter comprising plug and socket members provided with cooperating contacts, said plug member being tubular and having a fusible element contained therein and connecting said contacts, the wall of said tubular plug member containing a radially freely slidable member, said socket member being provided with an annular depression, said slidable member being freely movable radially outwardly towards engagement with said annular depression by the fluid pressure of air and gases generated within said tubular plug member upon severance of said fusible member under arcing conditions, thereby locking said plug member in said socket member.

8. A circuit interrupter comprising plug and socket members provided with cooperating contacts, said plug member being tubular and having a fusible element contained therein and connecting said contacts, the wall of said tubular plug member having radially disposed passages, said socket member being provided with an annular depression, spherical members freely disposed within said passages and being movable radially outwardly for engagement with said annular depression by the fluid pressure of air and gases generated within said tubular plug member upon severance of said fusible member under arcing conditions, thereby locking said plug member in said socket member.

9. A circuit interrupter comprising plug and socket members provided with cooperating contacts, the plug member being tubular and having a-fusible element contained therein and connecting said contacts, said fusible element being normally biased towards severance by a transversely expansible resilient member, the wall of said tubular plug member containing a radially slidable member, said socket member being provided with an annular depression, said slidable member being freely movable radially outwardly towards engagement with said annular depression upon contact with said resilient member on transverse expansion of said member after severance of said fusible element, said slidable member further being responsive to fluid pressure of air and gases generated within said tubular plug member for engagement with said annular depression upon severance of said fusible member under arcing conditions, thereby locking said plug member in said socket member.

10. A circuit interrupter comprising plug and socket members provided with cooperating con,- tacts, the plug member being tubular and having a fusible element contained therein and connecting said contacts, said fusible element being normally biased towards severance by a transversely expansible resilient member, the wall of said tubular plug member having radially disposed passages, said socket member being provided with anY annular depression, spherical members freely disposed within said passages and being movable radially outwardly for engagement with said annular depression upon contact with saidfresilient; member on transverse expansion of said member after severance of said fusible element, said spherical members further being responsive to uid pressure of air and gases generated within said plug member upon severance of said fusible member under arcing conditions, thereby locking said plug member in said socket member.

11. A circuit interrupter comprising plug and socket members provided With cooperating contacts, said plug member being tubular and having a fusible element contained therein and connecting said contacts, said fusible element being normally biased towards severance by a tensioned coil spring, the wall of said tubular plug member having radially disposed passages, said socket member being provided with an annular depression, spherical members freely disposed within said passages and being movable radially outwardly for engagement with said annular depression on Contact with the convolutions of said coil spring on retraction of said spring after severance of said fusible element, said spherical members further being responsive to iuid pressure of air and gases generated within said tubular plug member for engagement with said annular depression upon the severance of said fusible member under arcing conditions, thereby locking said plug member in said socket member.

EDWARD C. GRONOWSKI.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,108,993 Ramsey Feb. 22, 1938 2,392,308 Brown Jan. 8, 1948 2,410,243 Schultz Oct. 29, 1946 

